|By Ben Forta||
|July 11, 2001 12:00 AM EDT||
More ColdFusion applications are running on intranets and extranets than just about anywhere else. This is not surprising - as ColdFusion makes data access and reporting so simple it is a natural fit for applications in these environments. And, as such, data reporting is one area that ColdFusion 5 addresses head-on with the introduction of a true graphing engine.
ColdFusion developers have always wanted a way to graph data. And so back in Cold-Fusion 2 days, a series of Java applets were introduced to simplify the creation of common business graphs (pie charts, bar charts, etc.). These worked, but they had some serious limitations:
- They were Java applets, and as such were not supported by all browsers.
- They suffered from long download times and poor performance.
- They could not be printed easily.
And Generator does not need any client-side software because the file formats it creates are standard formats like JPEG (which are supported by all browsers automatically) - the only exception to this is Flash, the use of which is optional (although with over 96% of all browsers supporting Flash it is pretty standard too).
Now before you ask, no, you cannot (yet) extend or enhance the graphing features exposed to ColdFusion. Yes, Generator can do much more than has been made available at this time, and, at some point in the future, there likely will be a way to better utilize more of Generator within ColdFusion. But for now you have to use the charts and graphs explicitly defined in ColdFusion - and, fortunately, they'll do most of what you need, as you are about to see.
The <CFGRAPH> Tag
As you have come to expect of ColdFusion, the way you create graphs is by using a tag. And as you've also come to expect, that tag is intuitively named <CFGRAPH>. This seemingly simple tag hides all the complexity of creating all sorts of business graphs and charts with all sorts of options and features.
But instead of telling you about <CFGRAPH>, let's look at an example. Figure 1 shows a simple bar chart showing the relative prices of items for sale. (All of the data in these examples are taken from the databases and example applications in my new ColdFusion 5 Web Application Construction Kit.)
The code I used to create the graph is in Listing 1.
First I retrieved data with a basic <CFQUERY> - the query name is Merchandise, and the two columns retrieved are MerchName and MerchPrice. To create the graph, all I had to do was pass that data to <CFGRAPH> - QUERY takes the name of the query to be used, TYPE specifies the graph type (BAR, PIE, AREA, etc.), ITEMCOLUMN takes the name of the query column to use as the item name, and VALUECOLUMN takes the name of the column containing the value to use. Simple as that, and ColdFusion does the rest.
Note: ITEMCOLUMN and VALUECOLUMN take column names, not values, so don't place pound signs around the column names.
So what did that tag actually do? In Listing 2 is the code that was embedded in the generated output. I know it looks a little complex, but that is because it is invoking the Flash player so as to display the above graph in Flash format. In other words, the four lines of ColdFusion code in Listing 1 generated and embedded Flash content - without you having to learn anything about Flash.
And, no, you are not limited to generating Flash-based graphs. <CFGRAPH> can also generate JPEG and PNG images (not GIF though, sorry). But as I did not specify a format in my <CFGRAPH> tag, the default format was used, and the default is Flash.
Lots of Options
The previous example used a minimal set of options and attributes. This next example, in Listing 3, is quite the other extreme, using all sorts of attributes (far more than you'd typically use, but it helps make a point).
Again, I started with a <CF-QUERY>, this time retrieving recent items sold and a count of each. Then comes the <CFGRAPH> tag. The type is specified as PIE, the query name is provided; the format is set to "jpg" (otherwise the default of Flash would have been used); and explicit height and widths are specified along with background and border colors, border size, and 3D depth. And finally, label font and size, title text and font, and legend position and font are specified. The end result is seen in Figure 2.
As you can see, <CFGRAPH> is very flexible and highly configurable. And the Tag Editor seen in Figure 3 (available for ColdFusion Studio 4.5x as well as in ColdFusion Studio 5 when it is available) makes using these attributes a breeze.
One other very important feature that I must mention is the ability to generate graphs that support data drill-down - that is, click on a pie slice or chart bar and go to a URL that provides additional (or more detailed) information.
<CFGRAPH> does not do this automatically, but it does provide a simple mechanism for associating URLs with graph components. Using this you can create your own drill-down interfaces by simply passing the URL of the next chart or graph to go to (see Listing 4).
This time the query retrieves a list of directors, and what they have been paid (converted into thousands by a division in the SELECT statement itself). The <CFGRAPH> tag is similar to the ones seen previously, although this one provides explicit colors (instead of using the defaults).
The important changes here are the last two attributes. URL takes the URL to go to if you click on a pie slice. But if the same URL is used for all slices, how would you know which slice was clicked? That's where the URLCOLUMN attribute comes in to play. It takes the name of a column, the value of which is appended to the URL specified in URL.
Here "details.cfm?- Name=" is the URL, and Name (whatever value is in column Name) is the URLCOLUMN. So, if the name were "Ben Forta" the generated URL for that slice would be "details.cfm?-Name=Ben+Forta". In other words, a unique URL is created for each slice by combining the fixed URL and a dynamic query column (see Figure 4).
Data drill-down is a valuable <CFGRAPH> feature, but it is important to note that it's available only when using Flash as the FORMAT (and not with JPG or PNG).
For Even Greater Control
You might have been wondering why <CFGRAPH> has a matching </CFGRAPH> tag. Well, this is why - <CFGRAPH> has a child tag named <CFGRAPHDATA> that can be used to explicitly populate graphs with data (without using the QUERY attribute). For example, the following creates a pie chart containing four pie slices:
<!--- Create graph --->
<!--- Pie slices --->
<CFGRAPHDATA ITEM="G" VALUE="7">
<CFGRAPHDATA ITEM="PG" VALUE="28">
<CFGRAPHDATA ITEM="PG13" VALUE="16">
<CFGRAPHDATA ITEM="R" VALUE="31">
Of course, you can also use <CF-GRAPHDATA> to populate a graph with query data - to do this simply use a <CFLOOP> to loop through the query results and then call <CF-GRAPHDATA> for reach row like this:
<!--- Create graph --->
<!--- Loop through data --->
<!--- Add item to graph --->
<CFGRAPHDATA ITEM="#Name#" VALUE="#Paid#">
Why would you ever want to do this? There are three primary reasons:
- <CFGRAPHDATA> takes an optional URL attribute that you can use to specify a totally unique URL for each data point (as opposed to using a single URL with just a different query string).
- <CFGRAPHDATA> takes an optional COLOR attribute that you can use for greater color control.
- By passing data manually to graphs you can use CFML formatting functions and other programmatic functions to manipulate the data as needed.
<CFGRAPH> is one of the most exciting new features in ColdFusion 5, and one that is built on top of a proven and scalable product - Macromedia Generator. With multiple graph types, three output formats, and dozens of configuration options, <CFGRAPH> proves once again that Macromedia and the ColdFusion team know what developers want, and are deeply committed to providing it.
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